Surgical technique Routine preoperative preparations are carried out as for conventional percutaneous surgery. Under general anesthesia and with the patient in the lithotomy position, an open-ended 5F ureteral catheter is advanced into the renal pelvis under direct vision. The patient is then turned into the prone position. Percutaneous access is achieved using an 18-gauge coaxial needle to puncture the selected calyx under fluoroscopic or ultrasonic guidance. The success of the puncture is confirmed both by the free flow of the irrigation fluid and by fluoroscopic images. Using a guidewire, the dilatation is carried out with 10 F fascial dilators. Thenan irrigation-suction straight sheath, with the obturator, is advanced over the guidewire and introduced into the pelvicalyceal system. The guidewireis then removed, and the "handle" is connected to the straight sheath. The irrigation port of the irrigation-suction sheath is connected to an irrigation pump. The oblique tube of the sheath is connected to the specimen collection bottle, and the bottle then to the negative pressure aspirator. The irrigation fluid pressure is set as 200-250 mmHg. The suction pressure is controlled to a setting of 100-150 mmHg. The irrigation is delivered through the irrigation channel of the sheath. Thus, a one-way flow is created as the inflow that comes out of the irrigation channel of the sheath is immediately aspirated through the suction conduitof the sheath. Stone fragmentation is accomplished using either holmium laser or pneumatic lithotripter. The tiny pulverized stone fragments will pass around the scope and evacuate through the oblique sluice. If the stone fragments are too large to pass around the scope inside the sheath, the scope can be withdrawn slowly to proximal to the bifurcation in order to create an unobstructed channel for larger fragments evacuation. At the end of the procedure, a single fluoroscopic image is obtained to assess the stone-free status. A Double-J stent is placed only when there is the presence of an obstructing inflammatory ureteric edema, ureteropelvic junction obstruction, or concurrent treatment of ipsilateral ureteric stone with rigid ureteroscope. The sheath is removed, and the wound is either sutured or seal with absorbable gelatin. For patients with significant bleeding or extravasation, a nephrostomy tube is placed.